Help! White Spots on Poly

[buildintechie]

Hello all-
I'm working on finishing my coffee table, and after applying the first coat of Minwax Polyurethane on the sides of it, I've developed a number of white spots all over the piece. I've attached a picture for an example. I've been sanding with 280 grit after I stain prior to applying the poly...and applying it with a staining pad. I've finished the tops with this same method and they look great! After the 1st coat I sand with 320, and apply a 2nd, sand with 320, and apply a 3rd where needed.

What is this, and how can I get rid of them?

Thanks a ton!!!!!!!!!!!!!!!

 

[CrealBilly]

Hello all-
I'm working on finishing my coffee table, and after applying the first coat of Minwax Polyurethane on the sides of it, I've developed a number of white spots all over the piece. I've attached a picture for an example. I've been sanding with 280 grit after I stain prior to applying the poly...and applying it with a staining pad. I've finished the tops with this same method and they look great! After the 1st coat I sand with 320, and apply a 2nd, sand with 320, and apply a 3rd where needed.

What is this, and how can I get rid of them?

Thanks a ton!!!!!!!!!!!!!!!

Can't tell from the pics - but it could be glue or a really thick glob of poly. Are you spraying or brushing or both? Did you thin the poly down?

 

[buildintechie]

Its the prethinned stuff by Minwax, so no. Its not glue, I'm positive of that. It feels the same thickness as the rest of the piece.

I'm getting near the bottom of the can...could I have picked up something from the bottom of it that had settled?

 

[FredP]

Its the prethinned stuff by Minwax, so no. Its not glue, I'm positive of that. It feels the same thickness as the rest of the piece.

I'm getting near the bottom of the can...could I have picked up something from the bottom of it that had settled?

is this gloss or satin? satin has solids that make the finish dull. they settle, so frequent stirring is a must. get a fresh can, scrape the old off and redo. I always use gloss and dull it with steel wool. satin finishes [because of the solids] tend to hide the grain of the wood.

 

[buildintechie]

Semi-Gloss.


So should I just sand it down to wood and start it over?

 

[FredP]

Semi-Gloss.


So should I just sand it down to wood and start it over?

yep. i would get a new can of finish. water from condensation will also do this. partial cans will attract moister from changes in temperature and humidity.

 

[Canuck]

Jeff

I had what sounds like exactly the same issue while finishing a QSRO toy box early this year.

(Here is my original thread, albeit closed....http://www.ncwoodworker.net/forums/showthread.php?t=36623&page=2)

I ended up resanding the old finish off, restaining...making sure it was good and dry, applied a coat of dewaxed clear shellac to seal and then the coats of wiping varnish.

We narrowed my issue down to either a.)stain was not completely dry before adding the poly topcoat, b.)contaminated surface before applying finish or c.) not thoroughly stirring my can of satin wiping varnish.

Lesson learned for me. I lay down a coat of clear shellac over stained pieces as a sealer before my final topcoat,

Good luck and I know how frustrating this can be .....I have the T-shirt!:wsmile:

Wayne

 

[buildintechie]

It must be from not stirring the poly enough...I stained the pieces 3-4+ weeks ago. I'm very careful to remove all the sanding contaminants. I'll sand the finish off and refinish.

Thanks

 

[buildintechie]

As a follow-up, turns out the spots were from solids that had collected at the bottom of the can. I took a piece of scrap wood, gobbed some solids on a rag and wiped it on....let it dry for 2 days and came back...exact same spots, just bigger.

I was pretty good about stirring, but I guess if I use Minwax poly again, I'll stop using it once I hit 1/4 can to stay on the safe side.